Some strange behaviour in Redis

[Prince Philip]

Hi,

I have taken the redis-cli.c and modified it to work as a Loader tool.

I made two tools - one loader which will do INCR for a key - key123

and another tool Monitor which will do GET on key123

And the load I pump is around 5000 INCR/sec to Redis Server. No pipelining.

Both at Loader and Monitor tool I do frequent print of current time and latest value of key

What I have observed is that at time T1, the Loader print key value as 4000, but Monitor print key value as 4013.

How it can happen?

I know that Redis is single threaded and all operations are atomic.

My Loader and Monitor code is exactly same except one do INCR and other do GET.

Any specific reason for this?

rgds,

Prince

[CharSyam]

loader and monitor are different processes?

so how do you guarantee they are on same position?

I think upload your loader and monitor source.

and if you use some fuctions like printf, it can be buffered.

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[Jan-Erik Rediger]

Without seeing your code or knowing what you actually modified it's
impossible to say what's going on, so let me just guess:

The GET occurs after more INCR commands hit the server already and thus
the value is already higher.

[Greg Andrews]

When you say "Loader ... [does] frequent print of current time and latest value of key."

What does the print action do?  Print to stdout?  Print to a log file?  Are you sure the buffering between the code calling print() and your terminal screen cannot account for the 13 increments in the key?

  -Greg